TWI798287B - Manufacturing method of MI element and MI element - Google Patents

Abstract

The present invention provides a method for manufacturing an MI element and the MI element: by increasing the film thickness of the metal film, the cross-sectional area of the current path of the current flowing through the electromagnetic coil is ensured, so that the performance of the MI element can be ensured. The manufacturing method of the MI element 1 includes: an insulating step, forming an insulator layer 3 on the outer periphery of the amorphous wire 2; an electroless plating step, forming an electroless plating layer 4 on the outer peripheral surface of the insulator layer 3; an electrolytic plating step, on Form the electrolytic plating layer 5 on the peripheral surface of the electroless plating layer 4; resist step, form a resist layer R on the peripheral surface of the electrolytic plating layer 5; Exposure is performed to form a spiral groove portion GR on the outer peripheral surface of the resist layer R; and an etching step is performed using the resist layer R as a masking material to etch to remove the electroless plating in the groove portion GR. Layer 4 and electrolytic plating layer 5 , and coil 6 is formed from the remaining electroless plating layer 4 and electrolytic plating layer 5 .

Description

Manufacturing method of MI element and MI element

The present invention relates to a method for manufacturing an MI element and the MI element, and specifically relates to a technique for simplifying the configuration of equipment for manufacturing an MI element.

Previously, a magneto-impedance (Magneto Impedance: MI) element is known, which includes: a magneto-sensitive body including an amorphous wire (Amorphous wire); and an electromagnetic coil wound around the magneto-sensitive body via an insulator (for example, refer to patent Literature 1). The above-mentioned patent document describes a technique in which a metal material including copper is vacuum-deposited on the outer periphery of an insulator to form a metal film, and then an electromagnetic coil is formed by selective etching.

[Prior art literature]

[Patent Document]

[Patent Document 1] Japanese Patent No. 3781056

Like the above-mentioned prior art, when vacuum evaporation is used for forming the metal film, it is difficult to increase the film thickness of the metal film. When the thickness of the metal film in the MI element is small, the current path cross-sectional area of the current flowing through the electromagnetic coil cannot be sufficiently ensured, and the performance of the MI element may become insufficient.

The present invention is made in view of the above circumstances, and the problem to be solved by the present invention is to provide a method of manufacturing an MI element and an MI element: by forming the film thickness of the metal film to be large, the flow through the electromagnetic coil can be ensured. The current cross-sectional area of the current can ensure performance.

In order to solve the above-mentioned problems, the present invention provides a method of manufacturing an MI element and an MI element having the following configurations.

The manufacturing method of the MI element of the present invention comprises: an insulating step, forming an insulator layer on the outer periphery of the amorphous wire; an electroless plating step, forming an electroless plating layer on the outer peripheral surface of the insulator layer; an electrolytic plating step, on An electrolytic plating layer is formed on the outer peripheral surface of the electroless plating layer; a resist step is formed on the outer peripheral surface of the electrolytic plating layer; a resist layer is formed on the outer peripheral surface of the electrolytic plating layer; exposing the resist layer to form a spiral channel portion on the outer peripheral surface of the resist layer; and an etching step of etching the resist layer as a masking material to remove the channel The electroless plating layer and the electrolytic plating layer in the part, whereby a coil is formed from the remaining electroless plating layer and the electrolytic plating layer.

According to this configuration, the performance of the MI element can be ensured by ensuring a cross-sectional area of a current path of a current flowing through the electromagnetic coil by forming the thickness of the metal film large.

In addition, the manufacturing method of the MI element preferably includes a covering step of covering the coils formed in the etching step with a resin layer and filling resin between the coils.

According to this configuration, it is difficult for the coil to break away.

In addition, in the method of manufacturing the MI element, it is preferable that in the insulating step, the thickness of the insulator layer is formed uniformly in the circumferential direction.

According to this configuration, the sensitivity of the MI element can be improved.

In addition, in the method of manufacturing the MI element, it is preferable that in the insulating step, both ends of the amorphous wire are exposed from the insulator layer, and in the electroless plating step, the electroless plating The layer is formed so as to be in contact with both ends of the amorphous line, and in the exposure step, the channel portion is formed, and the A pair of ring-shaped grooves that are spaced apart and surround the resist layer. In the etching step, the electroless plating layer and the An electrolytic plating layer is formed as an electrode of the amorphous wire, and the electroless plating layer and the electrolytic plating layer remaining between the pair of annular grooves are formed as the coil, and the coil is Both ends are formed as ring-shaped coil electrodes that go around the insulator layer.

According to this configuration, since the coil electrode can be formed in a ring shape around the insulator layer, it can be mounted on the substrate regardless of the posture of the MI element.

In addition, the MI element of the present invention is an MI element including an amorphous wire, an insulator layer formed on the outer periphery of the amorphous wire, and a coil formed spirally on the outer peripheral surface of the insulator layer, and the coil is formed of The electroless plating layer and the electrolytic plating layer formed on the outer peripheral surface of the electroless plating layer are formed in two layers.

According to this configuration, the performance of the MI element can be ensured by ensuring a cross-sectional area of a current path of a current flowing through the electromagnetic coil by forming the thickness of the metal film large.

In addition, in the MI element, it is preferable that the coils are covered with a resin layer and resin is filled between the coils.

According to this configuration, the coils can be hardly detached because the resin enters between the coils.

In addition, the MI element is preferably formed so that the thickness of the insulator layer is uniform in the circumferential direction.

According to this configuration, the sensitivity of the MI element can be improved.

In addition, the MI element is preferably composed of both ends of the amorphous wire and an electroless plating layer covering the ends of the insulator layer and an electrolytic plating layer formed on the outer peripheral surface of the electroless plating layer. The electrodes formed by the two layers of the plating layer are connected.

According to this configuration, since the electrode of the amorphous wire can be formed from the electroless plating layer and the electrolytic plating layer remaining on the outer end side of the annular groove, the manufacturing process of the MI device can be simplified.

In addition, the MI element is preferably a ring-shaped coil electrode having both end portions of the coil formed around the insulator layer.

According to this configuration, since the coil electrode can be formed in a ring shape around the insulator layer, it can be mounted on the substrate regardless of the posture of the MI element.

According to the manufacturing method of the MI element and the MI element of the present invention, the performance of the MI element can be ensured by ensuring the cross-sectional area of the current path of the current flowing through the electromagnetic coil by forming the thickness of the metal film large.

1: Magnetic impedance element (MI element)

2: Amorphous wire

3: Insulator layer

4: Electroless plating layer

5: Electrolytic plating layer

6: Coil

7: Resin

8: Electrode

101: MI components

106: Coil

106C: coil department

106T: coil electrode

GP: Groove

GP1: Groove

GP2: Annular groove

GR: Groove

GR1: channel part

GR2: ring groove

R: resist layer

(a): Amorphous wire before insulation step

(b): The state after the insulation step

(c): The state after the electroless plating step

(d): The state after the electrolytic plating step

(e): The state after the resist step

(f): The state after the exposure step

(g): State after etching step

(h): The state after the resist removal step

(i): State after coating step

FIG. 1 is a plan view showing an MI element according to a first embodiment.

Fig. 2 is a sectional view taken along line II-II in Fig. 1 .

Fig. 3 is a sectional view along line III-III in Fig. 1 .

Fig. 4 is a diagram showing each manufacturing step of the MI device according to the first embodiment.

Fig. 5 is an enlarged cross-sectional view showing the surface portion of the MI element according to the first embodiment.

Fig. 6 is a plan view showing an MI element according to a second embodiment.

Fig. 7 is a sectional view taken along line VII-VII in Fig. 6 .

Fig. 8 is a diagram showing each manufacturing step of the MI device according to the second embodiment.

<MI element 1 (first embodiment)>

First, the configuration of a magneto-impedance element (hereinafter simply referred to as "MI element") 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3 . The MI element 1 performs magnetic induction by utilizing the so-called MI phenomenon in which an induced voltage is generated in the coil 6 in response to a change in current applied to a magnetosensitive body (amorphous wire 2 in this embodiment).

The MI phenomenon occurs with respect to a magnetosensitive body including a magnetic material having electron spin alignment in a peripheral direction with respect to a direction of a supplied current. When the energized current of this magnetosensitive body is suddenly changed, the magnetic field in the peripheral direction is changed rapidly, and due to the effect of the magnetic field change, the spin direction of electrons is changed according to the peripheral magnetic field. Moreover, the magnetosensitive body at this time The phenomenon in which changes in internal magnetization, impedance, etc. occur is the MI phenomenon.

As shown in FIGS. 2 and 3 , in the MI element 1 of the present embodiment, the amorphous wire 2 , which is a linear body having a circular outer peripheral shape such as CoFeSiB having a diameter of several tens of μm or less, is used as a magnetosensitive body. An insulator layer 3 that is an acrylic resin is formed on the outer periphery of the amorphous wire 2 so that the outer peripheral shape in a transverse cross section becomes a circular shape. Specifically, the outer peripheral shape of the insulator layer 3 is formed to be circular concentrically with the outer peripheral shape of the amorphous wire 2 , that is, the thickness of the insulator layer 3 is uniform in the circumferential direction. Specifically, the amorphous wire 2 is immersed in an electrodeposition paint in which an acrylic resin material is dispersed in an ion state in a solution, and a voltage is applied between the amorphous wire 2 and the electrodeposition paint in a tank, whereby ions State acrylic resin is electrodeposited on the amorphous wire. According to this method, the thickness of the insulating layer can be controlled by the applied voltage. The electrodeposition paint formed on the surface of the amorphous wire 2 in this manner is fired at a high temperature of, for example, 100 degrees or higher, thereby forming the insulator layer 3 .

A coil 6 is formed in a spiral shape on the outer peripheral surface of the insulator layer 3 . The coil 6 is formed of two layers of the electroless plating layer 4 and the electrolytic plating layer 5 formed on the outer peripheral surface of the electroless plating layer 4 . As shown in FIG. 2 , the coil 6 is covered with a layer of resin 7 except for both ends of the coil terminal, and the resin 7 is filled between the coils 6 . Thereby, the resin 7 enters between the coils 6, and it becomes difficult for the coil 6 to detach from the insulator layer 3.

Next, a method of manufacturing the MI element 1 will be described using FIG. 4 . In FIG. 4, (a) represents the amorphous wire 2 before the insulation step, (b) represents the state after the insulation step, (c) represents the state after the electroless plating step, and (d) represents the state after the electrolytic plating step state, (e) represents the state after the resist step, (f) represents the exposure step (g) shows the state after the etching step, (h) shows the state after the resist removal step, and (i) shows the state after the coating step.

When manufacturing the MI element 1 of this embodiment, as shown in FIG. 4( a ), an amorphous wire 2 , which is a wire body having a circular outer peripheral shape, is prepared. And, as shown in (b) in FIG. 4 , an insulator is applied to the outer periphery of the amorphous wire 2 to form an insulator layer 3 (insulation step). At this time, as shown in FIG. 3 , the outer peripheral shape in the cross section of the insulator layer 3 is formed to be a circular shape concentric with the outer peripheral shape of the amorphous wire 2 , that is, the insulator layer 3 The thickness is formed uniformly in the circumferential direction.

Next, as shown in (c) in FIG. 4 , electroless plating layer 4 is formed on the outer peripheral surface of insulator layer 3 by performing electroless Cu plating (electroless plating step). Furthermore, in this step, electroless Au plating can also be used. Next, as shown in (d) in FIG. 4 , the electrolytic plating layer 5 is formed on the outer peripheral surface of the electroless plating layer 4 by performing electrolytic Cu plating (electrolytic plating step). Furthermore, in this step, electrolytic plating of Au may also be used. Thus, in the present embodiment, the metal film is formed on the insulator layer 3 using electroless plating and electrolytic plating.

Next, after immersing the amorphous wire 2 formed with the electrolytic plating layer 5 in a photoresist bath containing a photoresist solution, it is pulled at a predetermined speed (for example, a speed of 1mm/sec), thereby A resist layer R is formed on the outer peripheral surface of the electrolytic plating layer 5 as shown in (e) of FIG. 4 (resist step).

Next, as shown in (f) in FIG. The spiral groove portion GR is formed on the outer peripheral surface of the resist layer R, and the electrolytic plating layer 5 of the groove portion GR is exposed (exposure step).

Exposure by laser in the exposure step is performed by rotating the central axis of the amorphous wire 2 on which the resist layer R is formed, and displacing it in the axial direction. In the present embodiment, a positive type photoresist is used in which a portion exposed to laser light is dissolved in a developing solution to form a spiral groove portion GR in the resist layer R. As shown in FIG. In addition, in this step, a negative photoresist in which a portion not exposed to laser light is dissolved in a developing solution to form a spiral channel portion in a resist layer can also be used.

Next, by immersing the amorphous wire 2 in which the groove portion GR is formed on the resist layer R in an acidic electrolytic polishing solution and performing electrolytic polishing, the resist remaining on the outer periphery of the electrolytic plating layer 5 is removed. layer as a masking material for etching. Thereby, as shown in (g) in FIG. 4, the electroless plating layer 4 and the electrolytic plating layer 5 of the part where the trench part GR was formed in the resist layer R are removed (etching process).

As shown in (g) of FIG. 4 , the spiral groove portion GP is formed in the portion where the groove portion GR is formed in the electroless plating layer 4 and the electrolytic plating layer 5 . That is, in this step, the remaining electroless plating layer 4 and electrolytic plating layer 5 are formed into the coil 6 .

Next, as shown in (h) in FIG. 4 , the resist layer R is removed using a stripper or the like (resist removal step). Then, after cutting the amorphous wire 2, the insulator layer 3, and the coil 6 to a predetermined length, as shown in (i) in FIG. Layer coating, and resin 7 is filled between the coils 6 (coating step).

As described above, in the manufacturing method of the MI device 1 of the present embodiment, When forming the metal film on the outer peripheral surface of the insulator layer 3 , electroless plating and electrolytic plating were used instead of vacuum vapor deposition. According to plating, it is easy to form the film thickness of the metal film large, so the current path cross-sectional area of the current flowing through the electromagnetic coil can be sufficiently ensured. That is, according to the manufacturing method of the MI element of this embodiment, the performance of the MI element can be ensured by securing the current path cross-sectional area of the electromagnetic coil.

In addition, when vacuum vapor deposition is used for forming the metal film, the chamber for accommodating the target object (insulator provided around the magnetosensitive body) needs to be in a vacuum state, so the equipment configuration becomes large-scale and the manufacturing cost increases. However, when electroless plating and electrolytic plating are used for forming the metal film as in this embodiment, a vacuum chamber or the like is unnecessary and the equipment configuration can be simplified, so that the manufacturing cost of the MI element 1 can be suppressed.

In addition, in the MI element 1 of the present embodiment, the coil 6 is covered with a layer of the resin 7 , and the resin 7 is filled between the coils 6 . Thereby, the resin 7 enters between the coils 6, and it becomes difficult for the coil 6 to detach from the insulator layer 3. Specifically, in the etching step, since etching is sequentially performed from the outside to the inside, the contact time of the etchant with the outer portion of the electrolytic plating layer 5 (the radially outer portion of the coil 6 ) becomes longer. Therefore, as shown in FIG. 5 , the outer portion of the electrolytic plating layer 5 is more etched and thinner than the inner portion. On the other hand, since the electroless plating layer 4 is denser than the electrolytic plating layer 5 , a large amount is etched and dented inward as shown in FIG. 5 . As a result, when the coil 6 is covered with the resin 7 in the covering step, the resin 7 is filled so as to be wound toward the electroless plated layer 4 side, and this part becomes a hooked shape. Thereby, a stronger anchoring effect can be obtained.

In addition, in the manufacturing method of the MI element 1 of the present embodiment, in the insulating step, the outer peripheral shape in the cross section of the insulator layer 3 is formed into a circular shape, thereby making the thickness of the insulator layer 3 uniform in the circumferential direction. form. Thereby, the distance between the amorphous wire 2 and the coil 6 formed on the outer peripheral surface of the insulator layer 3 can be made constant, and thus the sensitivity of the MI element 1 can be improved.

More specifically, in the technique described in Patent Document 1, the transverse cross section of the insulator layer is rectangular compared to the circular cross section of the amorphous wire. Therefore, depending on the position in the circumferential direction, the distance between the wire and the coil increases, and as a result, the sensitivity of the sensor decreases.

On the other hand, in the MI element 1 of this embodiment, the circular insulator layer 3 is formed on the surface of the amorphous wire 2 with a circular cross section, whereby the thickness of the insulator layer 3 is uniform in the circumferential direction. formed. Therefore, the distance between the amorphous wire 2 and the coil 6 can be made constant regardless of the position in the circumferential direction, and as a result, the sensitivity of the MI element 1 can be improved.

Furthermore, since the distance between the amorphous wire 2 and the coil 6 is fixed regardless of the position in the circumferential direction, the peripheral shape of the amorphous wire 2 and the insulating layer 3 need not be limited to a circular shape. For example, an insulator having a rectangular shape (specifically, a rectangular shape whose corners are chamfered to a rounded shape) may be similarly formed on the surface of an amorphous wire having a rectangular cross section so that the thickness thereof is uniform in the circumferential direction. layer. Even in this case, the distance between the amorphous wire and the coil can be fixed regardless of the position in the circumferential direction, and as a result, the sensitivity of the MI element 1 can be improved.

<MI element 101 (second embodiment)>

Next, the configuration of the MI element 101 according to the second embodiment of the present invention will be described using FIG. 6 and FIG. 7 . In this embodiment, the detailed description of the configuration common to the MI element 1 of the first embodiment will be omitted, and the description will focus on different configurations.

As shown in FIG. 7, also in the MI element 101 of this embodiment, the insulator layer 3 is formed on the outer periphery of the amorphous wire 2 similarly to the MI element 1 of the first embodiment. Furthermore, the coil 106 is spirally formed on the outer peripheral surface of the insulator layer 3 . The coil 106 is formed of two layers of the electroless plating layer 4 and the electrolytic plating layer 5 formed on the outer peripheral surface of the electroless plating layer 4 . In the MI element 101 of the present embodiment, both ends of the coil 106 are formed as a ring-shaped coil electrode 106T/coil electrode 106T that goes around the insulator layer 3 in the circumferential direction, and the spiral portion between the coil electrode 106T/coil electrode 106T is formed It is the coil part 106C. As shown in FIG. 6 , coil portion 106C of coil 106 is covered with a layer of resin 7 , and resin 7 is filled between coil portions 106C.

In addition, both ends of the amorphous wire 2 are formed of two layers: the electroless plating layer 4 covering the ends of the insulator layer 3 and the electrolytic plating layer 5 formed on the outer peripheral surface of the electroless plating layer 4 . The electrode 8/electrode 8 is connected.

Next, a method of manufacturing the MI element 101 will be described using FIG. 8 . In FIG. 8, (a) shows the amorphous wire 2 before the insulation step, (b) shows the state after the insulation step, (c) shows the state after the electroless plating step, and (d) shows the state after the electrolytic plating step state, (e) represents the state after the resist step, (f) represents the state after the exposure step, (g) represents the state after the etching step, (h) represents the state after the resist removal step, (i ) represents the state after the coating step.

When manufacturing the MI device 101 of this embodiment, as shown in (a) of FIG. 8 , the amorphous wire 2 cut into a predetermined length (several mm) is prepared. Then, as shown in (b) of FIG. 8 , an insulator such as silicon rubber is coated in a cylindrical shape on the outer periphery of the amorphous wire 2 to form an insulator layer 3 (insulation step). At this time, both ends of the amorphous wire 2 are exposed at both ends of the insulator layer 3 .

Next, as shown in (c) in FIG. 8, an electroless plating layer 4 is formed on the outer peripheral surface of the insulator layer 3 by performing electroless Cu plating (or electroless Au plating) (electroless plating step) . At this time, the electroless plating layer 4 is formed so as to be in contact with both ends of the amorphous wire 2 . Next, as shown in (d) of FIG. 8 , the electrolytic plating layer 5 is formed on the outer peripheral surface of the electroless plating layer 4 by performing electrolytic Cu plating (or electrolytic Au plating) (electrolytic plating step).

Next, after immersing the amorphous wire 2 formed with the electrolytic plating layer 5 in a photoresist bath containing a photoresist solution, it is pulled at a predetermined speed (for example, a speed of 1mm/sec), thereby A resist layer R is formed on the outer peripheral surface of the electrolytic plating layer 5 as shown in (e) of FIG. 8 (resist step).

Next, as shown in (f) in FIG. 8 , the resist layer R is exposed to laser light, and the part exposed to the laser light is dissolved using a developer, whereby the outer peripheral surface of the resist layer R is A spiral groove portion GR1 and an annular groove GR2 which is spaced from both ends of the groove portion GR1 on the outer side and surrounds the resist layer R are formed so that the groove portion GR1 and the annular groove The electrolytic plating layer 5 of GR2 is exposed (exposure step). Exposure by laser in the exposure step is performed multiple times by rotating the central axis of the amorphous wire 2 on which the resist layer R is formed, and displacing it in the axial direction.

Next, in the etching step, the amorphous wire 2 on which the channel portion GR1 and the annular groove GR2 are formed in the resist layer R is immersed in an acidic electrolytic polishing solution and electrolytic polishing is performed, thereby performing electrolytic polishing. The resist layer on the outer periphery of the plating layer 5 serves as a mask for etching. Thereby, as shown in (g) in FIG. step).

As shown in (g) of FIG. 8 , spiral groove portion GP1 is formed in the portion where groove portion GR1 is formed in electroless plating layer 4 and electrolytic plating layer 5 . Moreover, the annular groove part GP2 is formed in the part where the annular groove GR2 was formed. The electroless plated layer 4 and the electrolytic plated layer 5 are divided into a center portion forming the coil 106 and both end portions forming the electrode 8/electrode 8 by the annular groove portion GP2. That is, in this step, the electroless plating layer 4 and the electrolytic plating layer 5 remaining on the outer end side of the annular groove portion GP2 are formed as electrodes 8/electrodes 8 of the amorphous wire 2, The electroless plating layer 4 and the electrolytic plating layer 5 remaining between GP2 are formed into a coil 106 .

In the present embodiment, the groove portion GR1 and the annular groove GR2 are formed at a distance from each other, so the groove portion GP1 and the annular groove portion GP2 are formed at a distance from each other. Thus, both ends of the coil 106 are formed as ring-shaped coil electrodes 106T/106T that go around the insulator layer 3 , and the spiral portion between the coil electrodes 106T/106T is formed as a coil portion 106C.

Next, as shown in (h) in FIG. 8 , the resist layer R is removed using a stripper or the like (resist removal step). And, as shown in (i) in FIG. step).

According to the manufacturing method of the MI element 101 of the present embodiment, the electrode of the amorphous wire 2 is formed by the electroless plating layer 4 and the electrolytic plating layer 5 remaining on the outer end side of the annular groove portion GP2. 8/ Electrode 8 (both ends of the amorphous wire 2 are connected to the electrode 8 formed of two layers of the electroless plating layer 4 and the electrolytic plating layer 5 ). Therefore, the manufacturing process of the MI device 101 can be simplified without additionally forming electrodes.

According to the manufacturing method of the MI element 101 of the present embodiment, the coil electrode 106T/the coil electrode 106T can be formed in a ring shape around the insulator layer 3 . Therefore, the coil electrode 106T/coil electrode 106T can be made to face the substrate regardless of the posture of the MI element 101 , and thus can be mounted on the substrate.

1‧‧‧Magnetic impedance element (MI element)

2‧‧‧Amorphous wire

3‧‧‧Insulator layer

4‧‧‧Electroless plating layer

5‧‧‧Electrolytic plating layer

6‧‧‧coil

7‧‧‧Resin

Claims (9)

A method for manufacturing an MI element, comprising: an insulating step of forming an insulator layer on the periphery of an amorphous wire; an electroless plating step of forming an electroless plating layer on the outer periphery of the insulator layer; an electrolytic plating step of An electrolytic plating layer is formed on the outer peripheral surface of the electroless plating layer; a resist step is formed on the outer peripheral surface of the electrolytic plating layer; a resist layer is formed on the outer peripheral surface of the electrolytic plating layer; exposure to the resist layer to form a spiral channel portion on the outer peripheral surface of the resist layer; and an etching step of etching the resist layer as a masking material to remove the channel portion The electroless plating layer and the electrolytic plating layer form a coil with the remaining electroless plating layer and the electrolytic plating layer. The manufacturing method of the MI element as described in item 1 of the scope of the patent application, which includes a covering step, the covering step is to cover the coil formed in the etching step with a resin layer, and place the coil between the coils filled with resin. In the method of manufacturing an MI element according to claim 1 or claim 2, in the insulating step, the thickness of the insulator layer is uniformly formed in the circumferential direction. The method for manufacturing an MI element as described in claim 1 or claim 2, wherein in the insulating step, both ends of the amorphous wire are exposed from the insulator layer, In the electroless plating step, the electroless plating layer is formed in contact with both ends of the amorphous wire, and in the exposing step, the channel portion, and A pair of ring-shaped grooves spaced apart from both ends of the channel portion on the outer end side and surrounding the resist layer, and in the etching step, between the pair of ring-shaped grooves The electroless plating layer and the electrolytic plating layer remaining on the outer end side are formed as electrodes of the amorphous wire, and the electroless plating layer and the electroless plating layer remaining between the pair of annular grooves are formed as electrodes of the amorphous wire. The electrolytic plating layer is formed as the coil, and both ends of the coil are formed as ring-shaped coil electrodes that go around the insulator layer. An MI element comprising: an amorphous wire; an insulator layer formed on an outer periphery of the amorphous wire; and a coil formed spirally on an outer peripheral surface of the insulator layer, and in the MI element, the coil is It consists of two layers, a 1st layer and a 2nd layer formed in the outer peripheral surface of the said 1st layer. The MI element described in claim 5 of the present invention, wherein the coils are covered by a resin layer and resin is filled between the coils. The MI element according to claim 5 or claim 6, wherein the thickness of the insulator layer is formed uniformly in the circumferential direction. The MI element described in item 5 or item 6 of the scope of patent application, wherein Both ends of the amorphous wire are connected to electrodes formed of two layers: a first layer covering ends of the insulator layer and a second layer formed on the outer peripheral surface of the first layer. The MI element according to claim 5 or claim 6, wherein both ends of the coil are formed as ring-shaped coil electrodes that go around the insulator layer.

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